The hammerhead flatworms pose a serious threat to wildlife as they are known to have a negative impact on many helpful soil critters.

Scientists have recently confirmed that a predatory worm, with a head like a battle axe, has been invading France for about two decades now.

The hammerhead flatworms, which can grow more than 1 foot (40 centimeters) in length, pose a serious threat to wildlife and they are known to munch on earthworms and other invertebrate prey.

So what are these flatworms and how did they end up in Europe.

Hammerhead flatworms have colorful bodies and are typically found only in the warm parts of Asia.

Sightings of these worms date back to 1999, however, this is the first time that researchers have studied these worms in detail.

The scientists have reported that flatworms can be introduced to foreign lands as soil stowaways in international plant shipments, according to Live Science. After an extensive study of sightings of this creature, they have concluded that there are five non-native species of giant hammerhead flatworms living in mainland France and in French overseas territories, including Caribbean French islands, French Polynesia and French Guiana.

The lead study author Jean-Lou Justine, who is a professor with the Department of Systematics and Evolution at the National Museum of Natural History in Paris, also said that the worms survived in France, especially in the south of the country, because of the wet summers and mild winters.

Hammerhead flatworms hunt through the soil and produce neurotoxin called tetrodotoxin to paralyse preys. They can also create a cocktail of disgusting bodily juices, which act as a defence technique. Justine recounted that once a colleague tried to put a flatworm in his mouth and he describes the incident as "one of the worst experiences of his life".

Entomologist Archie Murchie of Britain's Agri-Food and Biosciences Institute said, according to the Washington Post: "Invasive flatworms can have a major impact on other soil fauna…The authors are rightly cautious about the potential impact of the hammerhead flatworms." The worms are likely to have a negative impact on many helpful soil critters.